Industrial-type variable-speed centrifuge

ABSTRACT

This electric-powered, variable-speed, heavy-duty centrifuge having improved operating characteristics comprises an outer shell with loading aperture, removable cover means for the aperture, support means for the load to be centrifuged rotatably mounted within said shell and drive means exterior of said shell for rotating the support means. The drive means comprises a hydraulic motor operatively connected to the support means for rotating the same, a hydraulic pump for supplying hydraulic fluid under pressure to the hydraulic motor, a dynamoelectric motor operatively connected to the hydraulic pump to drive the same, a hydraulic fluid reservoir, interconnecting hydraulic lines, an adjustable hydraulic pressure controller limiting the pressure from the hydraulic pump so as not to exceed a predetermined value, and an adjustable hydraulic flow controller controlling the flow to said hydraulic motor so as not to exceed a predetermined maximum flow rate. Bypass lines and check and adjustable throttle valves automatically convert the hydraulic system at the end of a centrifuging cycle to a dynamic braking function. The smoothness of the rapid acceleration and deceleration permits the use of a low-cost, simplified removable load holder which requires no interlocking with the rotatable support means and is held in place by gravitational friction alone.

netted States Patent [191 Tiger-man INDUSTRIAL-TYPE VARIABLE-SPEED CENTRIFUGE [75] Inventor: Louis Tigerman, River Hills, Wis. [73] Assignee: Globe-Union Inc., Milwaukee, Wis. [22] Filed: June 4, 1971 [21] Appl. No.: 150,015

Primary ExaminerReuben Friedman Assistant ExaminerF. F. Calvetti Attorney-Pendleton, Neuman, Williams & Anderson 11 3,738,490 June 12, 1973 [57] ABSTRACT This electric-powered, variable-speed, heavy-duty centrifuge having improved operating characteristics comprises an outer shell with loading aperture, removable cover means for the aperture, support means for the load to be centrifuged rotatably mounted within said shell and drive means exterior of said shell for rotating the support means. The drive means comprises a hydraulic motor operatively connected to the support means for rotating the same, a hydraulic pump for supplying hydraulic fluid under pressure to the hydraulic motor, a dynamoelectric motor operatively connected to the hydraulic pump to drive the same, a hydraulic fluid reservoir, interconnecting hydraulic lines, an adjustable hydraulic pressure controller limiting the pressure from the hydraulic pump so as not to exceed a predetermined value, and an adjustable hydraulic flow controller controlling the flow to said hydraulic motor so as not to exceed a predetermined maximum flow rate. Bypass lines and check and adjustable throttle valves automatically convert the hydraulic system at the end of a centrifuging cycle to a dynamic braking function. The smoothness of the rapid acceleration and deceleration permits the use of a low-cost, simplified removable load holder which requires no interlocking with the rotatable support means and is held in place by gravitational friction alone.

23 Claims, 13 Drawing Figures PATENTEU 2975 SIEHIUFB INVENTOR LOU/5 TIGERMAN /I2M,ZM MAJ-- ATTORNEYS PAIENImJum 2 ma FIG. 6

INVENTOR L OU/S TIGER/MAN ATTORNEYS PATENIEBJJH 1 2 I973 FIG.

INVENTOR LOU/.5 TIGER/VAN ATTORNEYS INDUSTRIAL-TYPE VARIABLE-SPEED CENTRIFUGE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a large, variable-speed centrifuge for heavy industrial loads, said centrifuge having improved operating characteristics. More particularly, it relates to a versatile, heavy-duty, variable-speed industrial centrifuge having an improved electrichydraulic system for driving and braking characterized by reduced cycle times and freedom from overheating problems which would otherwise limit the number of start-ups and stops per unit time.

While the present invention will be described with particular reference to an advantageous embodiment designed specifically for centrifuging a plurality of lead-acid automotive batteries for removing forming acid therefrom, it should be understood that the invention is not limited thereto. It can also be readily adapted for centrifuging a wide variety of materials including, for example, wood pulp, leather, laundry and the like, for removal of moisture therefrom, as those skilled in the art will recognize in the light of the present disclosure.

2. Description of the Prior Art Industrial-type centrifuges for handling heavy industrial loads, e.g., 50 pounds or more at a radius of a foot or more, have long been used in industry and the problems associated therewith are well known. This is reflected in the large number of prior art patents, illustrative examples including U.S. Pat. Nos. 1,791,536, 2,261,936, 2,349,559, 2,551,838, 2,596,927, 2,752,044, and 2,984,965.

Convenience, cleanliness, power supply availability and safety considerations often dictate the use of multihorsepower dynamoelectric motors as the prime movers for the centrifuges. While such machines have proven adequate for said purposes, they have shortcomings which limit their flexibility and versatility and otherwise render them unsuitable for certain purposes.

For example, alternating current dynamoelectric machines can be efficiently designed for operation at substantially constant running speeds, e.g., 1,740 rpm when employing 60 Hertz three-phase power supply. To obtain speed variability with such motors, however, a number of problems are encountered, including high cost and complexity and even resort to rectification or direct current power sources with all the difficulties associated therewith.

Moreover, when starting up a multi-horsepower dynamoelectric motor and bringing it up to speed, tremendous start-up currents are encountered, resulting in intermittent heavy drains on the electrical system which must be coped with in the initial design of the system. Thus, the system, including wiring, conduits, switches, control boxes and associated equipment, must be over-sized to handle the abnormally large starting current drains. In addition, plants which generate their own electricity must size their generators accordingly but may still encounter serious voltage drops during periods of acceleration.

One prior art technique for coping with the problem of heavy current drains is the use of eddy current clutch drives. While helpful, they are costly and may require even larger electric motors to operate the clutch. While the peak current drains may be substantially reduced,

they are still very large during acceleration, and the motor typically operates continuously rather than just during the centrifuging cycle.

The mechanical jolts associated with direct-drive electric motors, particularly at start-up, must also be coped with in the mechanical design of the centrifuge, primarily the moving parts of the driving system. These mechanical jolts may also damage or necessitate the tying down or shock mounting of fragile rigid structures which are to be centrifuged or require the use of elaborate holders therefor.

The mechanical jolts may also lead to undesired slippage or vibration of product holders such as battery baskets which are set into the basket of the centrifuge and rely upon gravitational frictional engagement to prevent relative movement during acceleration and deceleration. Smoothness of acceleration and deceleration obviates the need for mechanical interconnections to avoid slippage and simplifies the loading and unloading of the centrifuge.

The high electric currents during start-up and speedup also result in rapid buildup of heat in the motor and severe and costly limitations on the number of operating cycles per unit time to prevent motor burnout. For example, certain prior art laundry centrifuges or extractors employing alternating current electric motors in the 12.5 15.0 horsepower range and without eddy current clutches are limited to a maximum of six starts per hour. For many operations such limitation represents a severe, if not prohibitive, economic penalty.

The temperature problems are aggravated if the dynamoelectric motor is employed for dynamically braking the centrifuge at the completion of the centrifuging cycle. As a result, rather than suffer the economic disability of still more stringent limitation on the number of starts per hour, heavy duty friction brakes without dynamicbraking are employed. The reliance on friction brakes alone, however, extends the braking period and adds other cost factors. In addition, all the energy dissipated upon braking of the centrifuge is lost, rather than conserved.

Furthermore, the operating characteristics of alternating current motors result in long accelerating periods, thus prolonging the cycle time and penalizing the operation. To offset this and cope with other factors, prior art centrifuges have been designed with larger electric motors than otherwise would be necessary.

In the case of prior art electric-hydraulic drives, such as exemplified by the disclosures of US. Pat. Nos. 2,695,103, 3,038,611 and 3,504,794, the systems lacked automatic controls or introduced a degree of complexity which militated against the desired simplicity of design. Further, they lacked fail-safe dynamic braking features considered desirable in high-speed rotating industrial machinery.

It is to these and other problems associated with industrial-type centrifuges that the present invention is addressed.

OBJECTS OF THE INVENTION It is therefore a general object of the present invention to cope with these and other problems associated with prior art, electric driven, heavy duty centrifuges. It is another general object to provide an electric powered, smooth-running, industrial-type centrifuge having infinitely" variable speed capabilities and improved start-up and braking characteristics.

It is another general object to provide an electricpowered heavy duty centrifuge which can be cycled more rapidly than prior art centrifuges. It is another general object to provide an electric-powered, industrial-type centrifuge having improved dynamic braking characteristics.

It is a more specific object to provide a variable speed, heavy-duty centrifuge employing a dynamoelectric machine as the prime mover and a low-cost, simple hydraulic pump-motor system as the power coupling to the centrifuge, said system being designed so that it can be assembled from standard off-the-shelf commercially-available components. It is another specific object to provide a simplified electric-hydraulic system for driving and braking centrifuges which lends itself to conversion of prior-art systems and features an automatic fail-safe braking arrangement. It is a further specific object to provide an electric-driven, smoothrunning, industrial-type centrifuge having infinitely variable speed capabilities, said centrifuge being free of overheating problems.

It is another specific object to provide an electric drive for a heavy duty centrifuge which reduces current surges and mechanical stresses during start-up without resort to eddy current clutch drives or the like. It is still another specific object to provide an electric drive for a centrifuge wherein accelerating forces are smoothly and evenly applied, minimizing the size of motor required and the stresses on the load. It is still another specific object in connection with a preferred embodiment to conserve, rather than dissipate, at least a portion of the kinetic energy of the spinning centrifuge for use in operating associated equipment or in subsequent centrifuging cycles.

It is still another specific object to provide a holder for centrifuge loads which in conjunction with a smoothly accelerating electric-hydraulic drive and a fail-safe, smoothly decelerating dynamic braking system requires no mechanical interlock with the rotating element and relies on gravitational forces for non-slip frictional engagement thereof. These and other objects of the present invention will become apparent as the detailed description proceeds.

SUMMARY OF THE INVENTION These objects are achieved in a particular embodiment by an electric-powered, variable-speed centrifuge comprising an outer shell with removable cover and support means or basket for the load to be centrifuged, the support means being rotatably mounted within the shell and accessible through the aperture. A drive means which is located exteriorly of the shell rotates the support means by means of a mechanical coupling such as a rotatably supported shaft passing through the shell.

The drive means comprises a hydraulic motor operatively connected to the support means for rotating the same by, for example, a V-belt drive, a hydraulic pump for supplying fluid under pressure to the hydraulic motor, a prime mover such as a dynamoelectric motor connected to the hydraulic pump to drive the same, a reservoir for hydraulic fluid, hydraulic lines interconnecting the hydraulic pump, the hydraulic motor and the reservoir and an adjustable hydraulic pressure controller and an adjustable hydraulic flow controller controlling the pressure and the flow rate in the line from the hydraulic pump.

For dynamic braking, preferably in combination with mechanical braking, a hydraulic line provides fluid communication between the reservoir and the hydraulic motor, this hydraulic line having a pressure-sensitive check valve disposed to open when the hydraulic pump is de-energized. In addition, an adjustable throttle valve is automatically inserted in the line between the hydraulic motor and the reservoir when the hydraulic pump is de-energized. Thus, in the braking mode, when the hydraulic pump is de-energized, the inertia of the rotating centrifuge drives the hydraulic motor as if it were a pump so as to pump hydraulic fluid directly from the reservoir through the throttle valve and back to the reservoir.

In this dynamic braking embodiment, the throttle valve can be adjusted to provide whatever back pressure is desired under normal braking conditions. To avoid excessive pressures and pressure surges, particularly upon switching from the driving or centrifuging mode to the braking mode, a pressure relief valve or bypass is preferably inserted in the line between the outlet of the hydraulic motor and the throttle valve. This has the additional advantage of limiting the hydraulic braking pressures, particularly when a combination of dynamic and mechanical braking is employed and a decrease in mechanical braking or mechanical brake failure occurs. In such event, the hydraulic braking pressure builds up only to the point determined by the setting of the relief valve. The braking cycle time is accordingly extended to achieve the requisite braking with such maximum hydraulic braking pressures. An increase in braking cycle time will be an indication of loss in mechanical braking efficiency and thus will call for necessary adjustments of the mechanical brake.

The materials of construction are, of course, selected or protected to reflect the type of service to which the centrifuge is to be subjected. In the embodiment employed for removal of forming acid (e.g., suifuric acid having a specific gravity range of about 1.075 to 1.150) from lead-acid wet cell batteries, for example, the use of stainless steel or equivalent in the fabrication of critical components is recommended. Such is well within the skill of the art in the light of the present disclosure.

The resulting combination, assembled from off-theshelf components, has a number of surprising advantages over the prior art electric-driven centrifuges. In addition to having an infinitely variable centrifuging speed, as desired, there is practically no limitation on the number of cycles in a given period of time. This results in part from the fact that the hydraulic reservoir acts in a sense as a large heat sink" with rapid heat dissipation characteristics and also at no time is an overload put on the electric motor. Under very aggravated heat conditions, a hydraulic fluid cooler can be readily added to increase heat dissipation.

Another unexpected benefit is the fact that a smaller electric motor can be employed despite the fact that it is no longer directly coupled to the rotating element of the centrifuge. Control is enhanced by the automatic fail-safe braking system. In addition, the centrifuge operates more smoothly with lower current surges and mechanical stresses and no overheating problems.

Simplified, removable product holders which are held in place by gravitational friction can thus be employed with no slippage. A preferred holder for the simultaneous centrifuging of a plurality of batteries may comprise, for example, a two-tiered, light-weight, lowcost, easily-loadable and unloadable assembly comprising spaced annular horizontal webs with upstanding DETAILED DESCRIPTION OF THE DRAWINGS, INCLUDING PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, a typical installation comrigid rod members pivotally supporting a plurality of 5 pris Centrifuge rotatable j Crane loading and spaced battery cradles, as shown in the drawings. The loaded assembly can be quickly inserted into or removed from the centrifuge to achieve high production rates and maximum utilization of facilities.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood from the following detailed description of a specific embodiment read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a diagrammatic floor plan of one embodiment of the centrifuge of the present invention for removing forming acid from lead-acid batteries, including associated equipment for rapidly loading and unloading a plurality of batteries;

FIG. 2 is a diagrammatic elevation view in further detail of the centrifuge and associated equipment of FIG.

FIG. 3 is a plan view of the embodiment of the centrifuge shown in FIG. 2 with the cover in the closed position;

FIG. 4 is an elevation view of the embodiment of the centrifuge shown in FIG. 2, the cover being shown in solid lines in the closed position and in dashed lines in the open position;

FIG. 5 is a schematic of the electric-hydraulic drive means for driving and braking the centrifuge of FIGS. 1-4;

FIG. 6 is a perspective view of a partly assembled battery holder for the centrifuge of FIGS. 1-4;

FIG. 7 is a fragmentary elevation view, partially in section, of the partially assembled battery holder of FIG. 6 in place on the rotatable support means of the centrifuge, so as to be frictionally rotated thereby;

FIG. 8 is a fragmentary plan view, partially in section, of the partially assembled battery holder of FIG. 6 in place on the rotatable support means of the centrifuge so as to be frictionally rotated thereby;

FIGS. 9-11 are fragmentary plan, front elevation and side elevation views, respectively, of a preferred form of battery cradle for the battery holder of FIGS. 6-8;

FIG. 12 is similar to FIG. 5 and presents a schematic of a modified and preferred form of the electrichydraulic drive means; and

FIG. 13 is also similar to FIG. 5 and presents a schematic of another embodiment of the electric-hydraulic drive means featuring a hydraulic accumulator.

It should be understood that the drawings are not necessarily to scale and that graphic symbols and diagrammatic representations are employed in some instances. It should also be understood that details shown in some figures may be omitted in other figures to facilitate illustration of still other details. Further, in some figures, mechanical details which have nothing to do with the essence of the present invention have been omitted for simplicity and economy of drawings. Thus, the drawings may depart in certain respects from appearances when visually observed. It should also be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein.

unloading table C, and support foundation D. In this exemplar a load of batteries in a battery holder is centrifuged in centrifuge A while a second battery holder E is being unloaded and loaded at table C. Upon completion of the centrifuging cycle, the load of centrifuged batteries is removed from centrifuge A by means of the jib crane B and rotated to table C for unloading while a load of uncentrifuged batteries is rotated from table C around to the centrifuge for repeat of the cycle.

Centrifuge A comprises outer housing or shell 10 and cover 12 (FIG. 2) hingedly supported thereon. Outer housing or shell 10 is resiliently mounted on support platform 14 by means of suspension assemblies 16, 18 and 20, the specific structures thereof not being part of the present invention. Acid removed from the batteries is drained from outer shell 10 via outlet 22, the effluent being received in an acid-resistant receptacle or trough (not shown) from which it is recovered for further use by means of acid return unit 24. The hydraulic pump and electric drive therefor, which are part of the centrifuge drive means and are discussed in connection with FIG. 5, are mounted on frame 26, the electrical controls and associated electrical circuitry being mounted on and within panel or cabinet 28.

Rotatable jib crane B comprises support platform 30, which is securely bolted to foundation D, upright stanchion 32, and pivotal housing 34, which is rotatably mounted on stanchion 32 by means of bearings not shown. Housing 34 supports jib 36 on which air hoists 38 and 40 are movably mounted for lifting and lowering the battery carriers. Air hoists 38 and 40 are controlled by pushbutton control boxes 42 and 44, respectively, the details thereof not being part of the present invention. The travel of air hoists 38 and 40 along jib 36 is limited by stops 45 and 46, respectively.

Table C comprises base 47, cylindrical upright 48 and circular platform 49, the particular design or configuration not being critical and not a part of the present invention. In fact, the battery holder E could merely be suspended from air hoist 40 adjacent a conveyor system handling the uncentrifuged and centrifuged batteries.

The centrifuge of FIG. 2 is shown in greater detail in FIGS. 3 and 4. This particular exemplar is the result of rebuilding and modifying an industrial type laundry centrifuge or extractor to incorporate the novel features of the present invention, e.g., a 54-inch, Class 330, extractor previously sold by The American Laundry Machinery Company (Cincinnati, Ohio) under the trademark NOTRUX.

Cover 12 is hingedly supported on shell 10 by means of hinges 51 and 52 on reinforcing ribs 53 and 54. Hinges S1 and 52 are affixed to hinge pin or shaft 55, the latter being pivotally mounted in hinge bearings 56 and 58 of shell 10. Cover 12 is opened and closed by means of double-acting air cylinder 60 which is pinned to shell 10 at pivot point 62. When the piston rod 64 of air cylinder 60 is extended by compressed air from a source not shown, it rotates lever arm 66 so as to move the cover to the open position illustrated by the dashed lines in FIG. 4. When piston rod 64 is retracted, the cover 12 is moved to the closed position. A safety latch or interlock 68 is provided so that the centrifuge cannot be activated unless the cover is closed tightly, the circuitry for same being indicated in FIG. 13 discussed hereinafter.

An aperture or window is provided in cover 12 so that the centrifuging operation can be observed, said aperture being closed by transparent plastic web 70. A water spray nozzle inlet line 72 is also provided so that a hose connection may be made whereby a water spray can be introduced into the centrifuge, if desired, when the cover is closed.

The support means for the load to be centrifuged, which will be discussed further in connection with FIGS. 7 and 8, is rotated by means of hub 74, the hub being keyed to a rotatably mounted upright spindle 76 (FIG. 7). The upper portion 74a of hub 74 provides braking surface for conventional friction brake bands (not shown). The brake bands surround the upper portion 74a and are spring-biased to the closed position. They are held open during the centrifuging cycle by means of an air cylinder. This arrangement provides a fail-safe mechanical (frictional) braking system.

The lower portion 74b of hub 74 comprises a sheave for three V-belts 78. They are driven by hydraulic motor 80 and three-belt sheave 82, which are mounted on frame 83. Frame 83 is rigidly secured to the underside of shell so that no undue slackening or tightening of the belts 78 occurs as the shell moves during the centrifuging operation, particularly in the event of an unbalanced load. The hydraulic motor and shell move as one unit.

In a preferred embodiment a circular counting plate 84 with one or more apertures therein adjacent the periphery is secured to the lower portion of hub 74 and passes between a light source and light sensor (not shown). The speed of rotation is determined by an electronic counter, which senses the number of light impulses or interruptions. These are converted to RPM for visual display on a centrifuge speed dial. A metal sensor may also be employed in the same manner, the sensor detecting the presence or absence of metal as the apertured disc or plate 84 rotates.

Electricity, air and water connections are provided by means ofjunction box 85. Convenient access to hub 74 and other components on the underside of shell 10 is provided by removing plates 86 (FIG. 4) of support platform, the resulting access space being depicted at 87 in FIG. 3.

Hydraulic motor 80 is rotated by means of hydraulic circuitry shown schematically in FIG. 5. Electric motor 88, e.g., a 10 HP, 1,740 RPM (60 Hertz, 220 volts) electric motor sold by The Louis Allis Co., Milwaukee, Wisc., under the trademark Pacemaker," directly drives hydraulic pump 90 via coupling 92. Hydraulic pump 90 may be a-conventional rotary pump such as sold by Racine Hydraulics & Machinery lnc., Racine, Wisc., under the name Supervane Pump. Hydraulic oil is drawn from reservoir 94 via line 96 and is pumped by pump 90 into hydraulic passageway or line 98, the maximum pressure therein being regulated by conventional pressure relief valve 100 and hydraulic return line 102. While a separate relief valve 100 is depicted in FIG. 5, it should-be recognized that the relief valve function may be integrated as part of hydraulic pump 90. in any event, the hydraulic pressure in line 9 8 is adjustably controlled so as not to exceed a desired maximum, e.g., 1,500 psi in a particular embodiment. This prevents overloading the electric motor at any time.

Hydraulic fluid from line 98 enters variable flow controller 104 which can be set at the desired flow rate by adjusting the flow rate knob thereon, the flow rate in turn determining the speed of hydraulic motor and thus the centrifuge A. Flow control 104 is preferably a temperature-stabilized, pressure-compensated flow control valve of the type already available commercially, e.g., from Racine Hydraulics & Machinery, Inc. The resulting pressure-controlled, flow-controlled hydraulic fluid from flow controller 104 passes via lines 106 and 108 to hydraulic motor 80 and returns to reservoir 94 via lines 110, bypass-throttle valve 112, line 114, filter 116 and line 118. Hydraulic fluid leakage in motor 80 is returned to the reservoir via line 119.

Hydraulic fluid may also be transmitted to hydraulic motor 80 from reservoir 94 by means of hydraulic line 120 and pressure-sensitive check valve 122. The check valve is disposed so that it will open when electric motor 88 and pump are de-energized and the hydraulic pressure in lines 106-108 is less than in line 120.

Hydraulic pressure sensor line 124 controls the position of the spool of bypass-throttle valve 112. When motor 88 and pump 90 are energized whereby the hydraulic fluid in line 106 is pressurized, the pressure is transmitted to valve 112 whereby the spring-loaded spool therein is displaced so that fluid in line 110 is bypassed to line 114. When motor 88 and pump 90 are de-energized whereby the hydraulic fluid in line 106 is no longer pressurized, the lack of pressure is sensed via line 124 whereby the spring-loaded spool in valve shifts so that a throttle valve, e.g., a restricted orifice or hydraulic choke, is introduced between hydraulic lines 110 and 114. This creates a substantial back pressure in line 110 and results in the desired dynamic braking. The throttle valve portion of valve 112 is adjustable whereby the back pressure can be adjusted to achieve the desired back pressure for a given set of conditions.

in a typical operating cycle, electric motor 88 is actuated so as to drive hydraulic pump 90 to force hydraulic fluid at a predetermined maximum hydraulic pressure and at a predetermined maximum flow rate to hydraulic motor 80 via line 98, pressure relief valve 100, flow controller 104 and lines 106 and 108. Exhaust hydraulic fluid from motor 80 is returned to reservoir 94 via line 110, valve 112 (in its bypass mode), line 114, filter 116 and line 118.

Upon completion of the centrifuging cycle, electric motor 88 is de-energized whereby pressurized fluid is no longer provided by pump 90. The inertia of the centrifuge, however, continues to rotate motor 80 by means of belt drive 82 whereby motor 80 now acts as a hydraulic pump. In this mode, the roles of lines 108 and 110 are reversed, that is, line 108 is now the suction line and line 110 is the pressure line. As a result, pressure-sensitive check valve 122 opens whereby fluid is drawn from the reservoir via line 120.

The drop in pressure in line 106 is also sensed by sensor line 124 whereby the spool of bypass-throttle valve 112 shifts so as to insert the throttle portion thereof between hydraulic lines 110 and 114. The resulting pressure buildup in line 110 retards rotation of motor 80 and thus provides dynamic braking to the centrifuge via belts 78. It is important to not that dynamic braking automatically occurs as soon as line 106 is no longer pressurized. Thus, even in the event of a power failure or power shutdown, which may result from air failure, dynamic braking takes over to halt the centrifuge a fail-safe system.

Those skilled in the art will recognize that by the proper setting of pressure relief valve 100 at a predetermined desired value, the acceleration forces applied to the centrifuge are smooth, constant and continuous until the centrifuge reaches the desired speed as set by flow controller 104. It also assures that electric motor 88 is not overloaded or subjected to excess heat buildup. Likewise, for a given set of conditions, the proper setting of the throttle portion of bypass-throttle valve 112 will provide constant decelerating forces. As a consequence, the load being centrifuged is smoothly brought up to speed and smoothly braked.

If, as preferred, dynamic braking is employed in conjunction with mechanical braking, any loss in mechanical braking effectiveness would result for a given throttle valve setting in greater pressures in line 110 and greater dynamic braking forces. This will be discussed further in connection with FIG. 12.

In the battery centrifuging embodiment of the present exemplar, the smoothness of operation is reflected in the simplicity, the light-weight construction and the uniqueness of the battery holder employed in the centrifuge.

Referring to FIGS. 6, 7 and 8, the simplified battery holder E of the present invention comprises annular plates 130 and 132 which are held in spaced relationship from one another by a first set of upstanding rigid rod members 134 (FIG. 7) which are substantially equally spaced adjacent the outer periphery and a second set of shorter upstanding rigid rod members 136 (FlG. 7) which are substantially equally spaced adjacent the inner periphery. Rod members 134 and 136 are welded or otherwise secured to the bottom of the lower plate 130 and extend through corresponding apertures in both plates 130 and 132.

The desired spacing is achieved by means of spacer collars 138 and 140, respectively, the spacing collars 138 on rods 134 providing the axes of rotation for the bushings of the battery cradles 143 on the lower level, the cradles to be described in detail in connection with FIGS. 9-11. Rods 134 extend above the upper plate 132 and a second spacer collar 142 thereon provides the axis of rotation for the bushings of the battery cradles 143 on the upper level. Nuts 144 and 146 secure rods 134 and 136 and their respective spacer members 138, 142 and 140 in the desired fixed relationship.

A series of inwardly and upwardly radiating, elongated support rods 148 are secured at the lower extremity to the underside of annular plate 130 and at the other extremity to a centrally disposed circular web 150 having a common axis with the annular support surfaces 130 and 132. Inverted U-member 152 is secured to web 150 by bolts 154 so as to provide a lifting loop by means of which the hooks of air hoists 38 and 40 vertically lift and lower the battery holder for insertion into and removal from the support means or basket of the centrifuge.

In the present exemplar, the support means comprises a basket having perforated cylindrical walls 160 reinforced by a series of bands 162. Centrally disposed hub 164 of the support means is secured to spindle 76 so as to be rotated thereby. Bottom plate 166 has an upraised portion 168 on which the annular plate 130 rests. As previously indicated, theacceleration and deceleration forces are so smoothly and evenly applied during the centrifuging cycle that gravitational friction alone is sufficient to maintain non-slip contact between upraised portion 168 and the contacting portion of plate 130. Thus, no additional mechanical interlocking is required.

Referring to FIGS. 9-11, battery cradles 143 comprise a lower horizontal web 172 having upstanding hub or bushing 174 through which pass spacer rods 138 or 142, whereby the battery cradles can be rotated thereon for loading and unloading. In practice, the eradles are successively rotated outwardly, as indicated in FIGS. 1 and 2, to permit the loading or unloading of the batteries. The cradles are then swung inwardly until they abut stops 176 (FIGS. 7 and 8). In this position the cradles 143 are disposed within the outer periphery of annular plates and 132 and thus freely pass within the centrifuge basket where they are confined during the cycle without further securing means. The rear extremity of web 172 is partly cut out to provide hand access space 178 whereby the battery, indicated by dashed lines 180, can be gripped for removal.

Battery 180 is laid on its side on cradle 143 with the uncovered vent or filling holes and terminals outwardly disposed when in the centrifuging position. While in this exemplar the batteries are centrifuged with battery covers on, they may also be centrifuged without such covers. In either case, the battery elements may be secured in place to resist displacement by the centrifugal forces.

The battery is retained within the cradle by means of front wall 182 and side panels or half-walls 184 and 186. Front wall 182 is appropriately apertured to permit unrestricted flow of the forming acid under the influence .of centrifugal forces. The acid so removed passes through the apertured basket into the centrifuge shell from which it is continuously drained.

So that there is no possibility of short circuiting the batteries as the result of contact of the terminal posts with the metal wall 182, lower bumper or spacer 188 and upper bumper or spacer 190 are bolted or otherwise secured to the rear face of wall 182. These bumpers are non-conductive, e.g., hard rubber, plastic, or the like, and may also serve to protect the battery surface. The upper and lower bumpers are spaced from each other so that the cell openings or vent holes are disposed therebetween and the forming acid is free to flow outwardly under the influence of the centrifugal forces. Upper bumper 190 is appropriately apertured at 192 and 194 whereby the battery terminals fit within the aperture without contacting wall 182.

The battery cradles are dimensioned to handle various battery sizes, one cradle size usually covering at least several battery sizes. The dimensions are also selected so that there is a minimum of lost space on the annular surfaces between successive battery cradles.

The modified and preferred form of electrichydraulic drive means illustrated in FIG. 13 is very similar to that of FIG. 5 and identical components bear the same reference numerals. The primary difference lies in the introduction of a pressure relief valve 200 in return line 110 so as to limit the pressure surges during the deceleration or braking cycle. Thus, for example, pressure relief valve 200 can be set at any desired pressure, e.g., 4,000 psi, so that any incipient increases above that pressure would result in hydraulic fluid being bypassed directly to reservoir 94 via line 202, tee joint 204 and line 206. This could occur, for example, should the mechanical brakes lose efficiency or fail. It could also occur momentarily when the braking cycle commences.

Bypass-throttle valve 208 acts in the same manner as the bypass-throttle valve 112 in FIG. 5. Thus, during a normal acceleration and centrifuging cycle, the hydraulic fluid returns to the reservoir from motor 80 via line 110, relief valve 200, line 210, bypass-throttle valve 208 (in the bypass mode), line 212, filter 116, line 214, tee 204 and line 206. In the deceleration or braking cycle, the same path is followed except that the spool of bypass-throttle valve is shifted to the throttle mode and, in the event of incipient excessive pressures, a portion of hydraulic fluid is diverted by relief valve 200 to the reservoir via line 202, tee joint 204 and line 206 to maintain the desired maximum pressure. As in the system of FIG. 5, dynamic braking occurs automatically when line 106 is not pressurized a fail-safe system.

To conserve at least a portion of the energy represented by the kinetic energy of the rotating centrifuge, a hydraulic accumulator may be added to the system, as depicted in FIG. 13. In a specific embodiment the accumulator system is tapped into return line 110 of either of the embodiments of FIGS. 5 or 12. With bypass-throttle valve 112' (FIG. 5) or 208 (FIG. 12) in the throttle mode during the braking cycle, pressurized hydraulic fluid is bypassed from line 110 via check valve 220 and line 221 to hydraulic accumulator 222 until the pressure therein approximately equals that in line 110. Check valve 220 prevents any backflow when the pressure in line 110 drops below that in accumulator 222.

Accumulator 222 may be a conventional bottle accumulator with varying pressure or, preferably, a weighted accumulator wherein large volumes of hydraulic fluid can be accumulated and delivered at substantially constant pressure. The hydraulic energy stored in accumulator 222 may be employed to assist in accelerating the centrifuge in subsequent cycles or for operating associated equipment, or both, as those skilled in the art will recognize in the light of this disclosure.

In the schematic embodiment of FIG. 13, for example, pressurized hydraulic fluid from accumulator 222 is delivered to the hydraulic motor 80 of FIGS. 5 or 12 via line 223, pressure reducing valve 224 (where 'pressure is reduced to 1500 psi in this embodiment) and appropriate control valvin g represented by valve 225. Accumulator operations must, of course, be interrelated with operations of pump 90, the primary source of pressurized hydraulic fluid for driving motor 80, as those skilled in the art will recognize.

Pressurized hydraulic fluid from accumulator 222 may also be employed to actuate hydraulic cylinders operating the friction brakes and the cover assembly of the centrifuge, thereby replacing air cylinders for such purposes in the embodiments of FIGS. 3 and 4. Hydraulic fluid from accumulator 222 passes via line 226, pressure reducing valve 227 (where pressure may be reduced to about 100 psi), line 228, check valve 229, solenoid control valve 230 and line 231 to brake cylinder 232, whereby rod 233 is retracted to release springbiased brake band 234 on centrifuge hub 74a. In this embodiment the brakes are spring-biased to the closed or braking position and are held open by activation of hydraulic cylinder 232 during the centrifuging cycle. The solenoid of valve 230 is electrically activated by circuitry 240 tied into the starter circuit of electric motor 88 (FIGS. 5 and 12) so that the friction brakes are released simultaneously as current is applied to the starter circuit. Upon commencement of braking, hydraulic fluid from cylinder 232 is returned to the reservoir 94 (FIGS. 5 and 12) via line 241.

Pressurized hydraulic fluid from accumulator 222 also passes via line 226, reducing valve 227, line 242, cover-close switch 244 and line 246 to hydraulic cylinder 248, piston rod 250 of which is mechanically linked to the cover 12 of the centrifuge. In this embodiment the centrifuge cover is spring-biased to the open position and is closed when pressurized hydraulic fluid enters cylinder 248. Hydraulic fluid can pass to cylinder 248 only when the close button 252 of cover-close switch 244 is manually pushed to the close position.

When cover 12 is opened, hydraulic fluid from cylinder 248 returns to reservoir 94 via line 254.

Electrical leads 240 form a series circuit which is tied in with the starter circuit of the electric motor 88, whereby the drive motor cannot be electrically activated until the cover-close switch is in the close position and cover-close detector switch 256 is closed. Switch 256 corresponds with the safety latch switch or interlock 68 previously described in connection with FIGS. 3 and 4. As previously indicated, current flow through circuitry 240 activates solenoid control valve 230 to release the friction brakes 234. There are still other important interlocks. For example, the centrifuge is provided with a no-speed switch (not shown) whereby the centrifuge must be completely stopped before the cover can be opened. When the cover is open there can be no current flow to the electric motor and therefore there can be no pressure in any hydraulic lines (assuming no accumulator).

When first starting up the centrifuge, that is, before accumulator 222 is pressurized, it may be necessary to manually release the centrifuge friction brakes and manually close the centrifuge cover. Otherwise it will be necessary to pressurize accumulator 222 from an auxiliary source or provide the requisite wiring, piping and valving whereby electric motor 88 and pump 90 can be employed for such purposes. In fact, motor 88 and pump 90 could keep the accumulator pressurized continuously, whereby hydraulic motor could be driven exclusively by pressurized hydraulic fluid from the accumulator.

Accumulating hydraulic energy in accumulator 222 during the braking cycle for use in subsequent cycles or for operating associated equipment has an additional advantage. The energy so employed represents energy which no longer need be dissipated by braking. In addition, the hydraulic fluid employed in the accumulator circuit increases the volume and thus the thermal capacity of the heat sink, rendering the heat dissipation problem in the system even less significant.

From the above description it is apparent that the objects of the present invention have been achieved. While only certain embodiments have been set forth, alternative embodiments and various modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of the present invention.

Having described the invention, what is claimed is: 1. An electric-powered, variable-speed centrifuge suitable for heavy industrial loads comprising in combination:

a. an outer housing with loading aperture; b. removable cover means for said aperture to provide access to the interior of said housing for loading and unloading purposes and to close said aperture during centrifuging operations; 0. support means for the load to be centrifuged, said support means being rotatably mounted within said housing and accessible for loading and unloading through said aperture; and d. drive means exterior of said housing for rotating said support means, said drive means comprising: 1. a hydraulic motor operatively connected to said support means for rotating the same, said bydraulic motor having a hydraulic inlet and outlet,

2. a hydraulic pump as a source of hydraulic fluid under pressure for said hydraulic motor, said hydraulic pump having a hydraulic inlet and outlet,

3. a prime mover operatively connected to said hydraulic pump to drive the same,

4. a reservoir for hydraulic fluid for said hydraulic pump and said hydraulic motor,

5. hydraulic passageways providing fluid communication between said reservoir and the inlet of said hydraulic pump, between the outlet of said hydraulic pump and the inlet of said hydraulic motor and between the outlet of said hydraulic motor and said reservoir,

6. an adjustable hydraulic pressure controller controlling the pressure in the hydraulic passageway to the inlet of said hydraulic motor so as not to exceed a predetermined maximum pressure,

7. an adjustable hydraulic flow controller in the hydraulic passageway to the inlet of said hydraulic motor controlling the flow rate to said hydraulic motor so as not to exceed a predetermined maximum flow rate, and

8. means for throttling the flow of hydraulic fluid from said hydraulic motor to said reservoir responsive to de-energization of said hydraulic pump.

2. The centrifuge of claim 1 wherein said adjustable hydraulic pressure controller comprises a hydraulic passageway bypassing hydraulic fluid from said hydraulic pump to said reservoir and an adjustable pressure relief valve diverting hydraulic fluid to the bypassing hydraulic passageway responsive to a predetermined adjustable maximum pressure at the outlet of said hydraulic pump. 7

3. The centrifuge of claim 1 including a hydraulic passageway providing fluid communication between said reservoir and the inlet of'said hydraulic motor and a pressure-sensitive check valve in this hydraulic passageway disposed to be openable when said hydraulic pump is de-energized.

4. The centrifuge of claim 1 wherein said means for throttling comprises an adjustable throttle valve insertable in the passageway between the outlet of said hydraulic motor and said reservoir responsive to the hydraulic pressure in the passageway from the outlet of said hydraulic pump, whereby said throttle valve is removed from the circuit when said hydraulic pump is energized and said throttle valve is inserted in the circuit when said hydraulic pump is de-energized.

5. The centrifuge of claim 4 wherein said means for throttling comprises a spring-biased hydraulic valve spool positioned in response to the hydraulic pressure in the passageway from the outlet of said hydraulic pump so as to insert said adjustable throttle valve into or remove said throttle valve from the hydraulic circuit.

6. The centrifuge of claim 4 including a pressure relief valve and bypass to said reservoir in the hydraulic passageway between the outlet of said hydraulic motor and said adjustable throttle valve.

7. The centrifuge of claim 1 including an accumulator which receives pressurized hydraulic fluid from the outlet of said hydraulic motor during dynamic braking of the centrifuge.

8. The centrifuge of claim 7 including friction brakes for retarding rotation of said support means and hydraulic cylinders controlling said brakes and said cover means, pressurized hydraulic fluid being supplied to said hydraulic cylinders from said accumulator.

9. The centrifuge of claim 1 including an accumulator for pressurized hydraulic fluid, said accumulator receiving pressurized hydraulic fluid from said hydraulic pump when the hydraulic pressure therein is less than a predetermined minimum value.

10. The centrifuge of claim 1 wherein said housing is resiliently mounted on a supporting foundation and said hydraulic motor is rigidly secured to said housing.

11. The centrifuge of claim 1 including counting means responsive to the rotation of said support means.

12. The centrifuge of claim 1 wherein said support means includes an upwardlyopen basket having cylindrical side walls with a plurality of perforations therein.

13. The centrifuge of claim 1 including a holder for a plurality of batteries, said holder comprising:

l. a normally horizontal first annular support surface having bottom portions which are disposed to rest on said support means so as to be rotated by fric-' tional engagement therewith,

2. a plurality of upstanding rigid rod members substantially equally spaced adjacent the outer periphery of said first annular support surface,

3. battery cradles pivotally mounted on said upstanding rods whereby said cradles can be pivoted outwardly beyond said first annular support surface to provide access for battery loading and unloading and inwardly for battery cradling and support during centrifuging, said battery cradles having at least a lower horizontal web for supporting the battery on its side, an upstanding wall disposed to counter centrifugal forces on the battery during centrifuging, and an upstanding bushing adjacent an edge of the lower horizontal web for pivotally mounting the cradles on said rod members, at least the upstanding wall having apertures therein to provide a fluid passageway for liquids passing out of the battery under the influence of centrifugal forces.

14. The centrifuge of claim 13 including stops on said first annular support surface to limit the pivotal movement of said battery cradles.

15. The centrifuge of claim 13 including a centrally disposed circular web having a common axis with said annular support surface, said web being disposed inwardly and upwardly of said annular support surface, a plurality of elongated rigid members connecting said circular web and said annular support surface, and a hook receiving member secured to said web whereby the battery holder can be vertically lifted as a unit.

16. The centrifuge of claim 13 wherein said battery support cradles have two upstanding partial walls on said lower horizontal web substantially perpendicular to and at the extremity of said upstanding wall, whereby a battery support pocket is formed.

17. The centrifuge of claim 13 including bumpers having electrical insulation properties secured to the inner surface of said upstanding wall to electrically isolate the battery terminals during loading, unloading and centrifuging.

18. The centrifuge of claim 13 wherein said battery holder includes at least a second annular support surface rigidly supported spacedly from said first annular support surface and having a common axis therewith, said second annular support surface having pivotally supported on upstanding rigid rod members thereof a plurality of battery cradles substantially identical to those on said first annular support surface, whereby a multi-tiered holder is provided.

19. The centrifuge of claim 18 wherein the upstanding rigid rod members of said first and said second annular support surfaces are common.

20. An electric-powered, variable-speed centrifuge suitable for heavy industrial loads comprising in combination:

a. an outer shell with loading aperture;

b. removable cover means for said aperture to provide access to the interior of said shell for loading and unloading purposes and to close said aperture during centrifuging operations;

c. support means for the load to be centrifuged, said support means being rotatably mounted within said shell and accessible for loading and un-loading through said aperture; and

d. drive means exterior of said shell for rotating said support means, said drive means comprising:

1. a hydraulic motor operatively connected to said support means for rotating the same, said bydraulic motor having a hydraulic inlet and outlet,

2. a hydraulic pump as a source of hydraulic fluid under pressure for said hydraulic motor, said hydraulic pump having a hydraulic inlet and outlet,

3. a dynamoelectric motor operatively connected to said hydraulic pump to drive the same,

4. a reservoir for hydraulic fluid for said hydraulic pump and said hydraulic motor,

5. hydraulic passageways providing fluid communication between said reservoir and the inlet of said hydraulic pump, between the outlet of said hydraulic pump and the inlet of said hydraulic motor and between the outlet of said hydraulic motor and said reservoir,

6. an adjustable hydraulic pressure controller controlling the pressure in the hydraulic passageway to the inlet of said hydraulic motor so as not to exceed a predetermined maximum pressure,

7. an adjustable hydraulic flow controller in the hydraulic passageway to the inlet of said hydraulic motor controlling the flow rate to said hydraulic motor so as not to exceed a predetermined maximum flow rate,

8. a hydraulic passageway providing fluid communication from said reservoir to the inlet of said hydraulic motor and a pressure sensitive check valve in said hydraulic passageway disposed to open when said hydraulic pump is de-energized,

and

9 an adjustable throttle valve insertable in the passageway between the outlet of said hydraulic motor and said reservoir responsive to the outlet pressure of said hydraulic pump, whereby said throttle valve is automatically removed from the circuit when said hydraulic pump is energized and said throttle valve is inserted in the circuit when said hydraulic pump is de-energized so as to provide dynamic braking of said hydraulic motor.

21. The centrifuge of claim 19 including an adjustable pressure relief valve in the passageway between the outlet of said hydraulic motor and said adjustable throttle valve.

22. The centrifuge of claim 21 including friction brakes for retarding rotation of said support means in cooperation with the dynamic braking of the hydraulic system, whereby a decrease in friction braking efficiency is reflected in prolongation of dynamic braking.

23. The centrifuge of claim 19 including a multitie red battery holder disposed on said support means so as to be rotated by frictional engagement therewith.

t a a:

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,738,490 Dated June l2 1973 Inventor(s) Louis Tigerman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 16, line 33, "l9" should be 20-.

Signed and sealed this 16th day' of April 19% (315m Atte st:

EDWARD 1 I.FLE'IUHER ,JR. G. IiAHSi-iALL DANN Attesting Officer Commissioner of Patents FORM PO- (10-69) USCOMM-DC eoave P69 Q U.S. GOVEFINMENY PRINTING OFFICE: I969 0-366-33l of 

1. An electric-powered, variable-speed centrifuge suitable for heavy industrial loads comprising in combination: a. an outer housing with loading aperture; b. removable cover means for said aperture to provide access to the interior of said housing for loading and unloading purposes and to close said aperture during centrifuging operations; c. support means for the load to be centrifuged, said support means being rotatably mounted within said housing and accessible for loading and unloading through said aperture; and d. drive means exteriOr of said housing for rotating said support means, said drive means comprising:
 1. a hydraulic motor operatively connected to said support means for rotating the same, said hydraulic motor having a hydraulic inlet and outlet,
 2. a hydraulic pump as a source of hydraulic fluid under pressure for said hydraulic motor, said hydraulic pump having a hydraulic inlet and outlet,
 3. a prime mover operatively connected to said hydraulic pump to drive the same,
 4. a reservoir for hydraulic fluid for said hydraulic pump and said hydraulic motor,
 5. hydraulic passageways providing fluid communication between said reservoir and the inlet of said hydraulic pump, between the outlet of said hydraulic pump and the inlet of said hydraulic motor and between the outlet of said hydraulic motor and said reservoir,
 6. an adjustable hydraulic pressure controller controlling the pressure in the hydraulic passageway to the inlet of said hydraulic motor so as not to exceed a predetermined maximum pressure,
 7. an adjustable hydraulic flow controller in the hydraulic passageway to the inlet of said hydraulic motor controlling the flow rate to said hydraulic motor so as not to exceed a predetermined maximum flow rate, and
 8. means for throttling the flow of hydraulic fluid from said hydraulic motor to said reservoir responsive to deenergization of said hydraulic pump.
 2. a plurality of upstanding rigid rod members substantially equally spaced adjacent the outer periphery of said first annular support surface,
 2. a hydraulic pump as a source of hydraulic fluid under pressure for said hydraulic motor, said hydraulic pump having a hydraulic inlet and outlet,
 2. a hydraulic pump as a source of hydraulic fluid under pressure for said hydraulic motor, said hydraulic pump having a hydraulic inlet and outlet,
 2. The centrifuge of claim 1 wherein said adjustable hydraulic pressure controller comprises a hydraulic passageway bypassing hydraulic fluid from said hydraulic pump to said reservoir and an adjustable pressure relief valve diverting hydraulic fluid to the bypassing hydraulic passageway responsive to a predetermined adjustable maximum pressure at the outlet of said hydraulic pump.
 3. The centrifuge of claim 1 including a hydraulic passageway providing fluid communication between said reservoir and the inlet of said hydraulic motor and a pressure-sensitive check valve in this hydraulic passageway disposed to be openable when said hydraulic pump is de-energized.
 3. a dynamoelectric motor operatively connected to said hydraulic pump to drive the same,
 3. battery cradles pivotally mounted on said upstanding rods whereby said cradles can be pivoted outwardly beyond said first annular support surface to provide access for battery loading and unloading and inwardly for battery cradling and support during centrifuging, said battery cradles having at least a lower horizontal web for supporting the battery on its side, an upstanding wall disposed to counter centrifugal forces on the battery during centrifuging, and an upstanding bushing adjacent an edge of the lower horizontal web for pivotally mounting the cradles on said rod members, at least the upstanding wall having apertures therein to provide a fluid passageway for liquids passing out of the battery under the influence of centrifugal forces.
 3. a prime mover operatively connected to said hydraulic pump to drive the same,
 4. a reservoir for hydraulic fluid for said hydraulic pump and said hydraulic motor,
 4. The centrifuge of claim 1 wherein said means for throttling comprises an adjustable throttle valve insertable in the passageway between the outlet of said hydraulic motor and said reservoir responsive to the hydraulic pressure in the passageway from the outlet of said hydraulic pump, whereby said throttle valve is removed from the circuit when said hydraulic pump is energized and said throttle valve is inserted in the circuit when said hydraulic pump is de-energized.
 4. a reservoir for hydraulic fluid for said hydraulic pump and said hydraulic motor,
 5. hydraulic passageways providing fluid communication between said reservoir and the inlet of said hydraulic pump, between the outlet of said hydraulic pump and the inlet of said hydraulic motor and between the outlet of said hydraulic motor and said reservoir,
 5. The centrifuge of claim 4 wherein said means for throttling comprises a spring-biased hydraulic valve spool positioned in response to the hydraulic pressure in the passageway from the outlet of said hydraulic pump so as to insert said adjustable throttle valve into or remove said throttle valve from the hydraulic circuit.
 5. hydraulic passageways providing fluid communication between said reservoir and the inlet of said hydraulic pump, between the outlet of said hydraulic pump and the inlet of said hydraulic motor and between the outlet of said hydraulic motor and said reservoir,
 6. an adjustable hydraulic pressure controller controlling the pressure in the hydraulic passageway to the inlet of said hydraulic motor so as not to exceed a predetermined maximum pressure,
 6. The centrifuge of claim 4 including a pressure relief valve and bypass to said reservoir in the hydraulic passageway between the outlet of said hydraulic motor and said adjustable throttle valve.
 6. an adjustable hydraulic pressure controller controlling the pressure in the hydraulic passageway to the inlet of said hydraulic motor so as not to exceed a predetermined maximum pressure,
 7. an adjustable hydraulic flow controller in the hydraulic passageway to the inlet of said hydraulic motor controlling the flow rate to said hydraulic motor so as not to exceed a predetermined maximum flow rate, and
 7. The centrifuge of claim 1 including an accumulator which receives pressurized hydraulic fluid from the outlet of said hydraulic motor during dynamic braking of the centrifuge.
 7. an adjustable hydraulic flow controller in the hydraulic passageway to the inlet of said hydraulic motor controlling the flow rate to said hydraulic motor so as not to exceed a predetermined maximum flow rate,
 8. a hydraulic passageway providing fluid communication from said reservoir to the inlet of said hydraulic motor and a pressure sensitive check valve in said hydraulic passageway disposed to open when said hydraulic pump is de-energized, and
 8. The centrifuge of claim 7 including friction brakes for retarding rotation of said support means and hydraulic cylinders controlling said brakes and said cover means, pressurized hydraulic fluid being supplied to said hydraulic cylinders from said accumulator.
 8. means for throttling the flow of hydraulic fluid from said hydraulic motor to said reservoir responsive to de-energization of said hydraulic pump.
 9. The centrifuge of claim 1 including an accumulator for pressurized hydraulic fluid, said accumulator receiving pressurized hydraulic fluid from said hydraulic pump when the hydraulic pressure therein is less than a predetermined minimum value.
 9. an adjustable throttle valve insertable in the passageway between the outlet of said hydraulic motor and said reservoir responsive to the outlet pressure of said hydraulic pump, whereby said throttle valve is automatically removed from the circuit when said hydraulic pump is energized and said throttle valve is inserted in the circuit when said hydraulic pump is de-energized so as to provide dynamic braking of said hydraulic motor.
 10. The centrifuge of claim 1 wherein said housing is resiliently mounted on a supporting foundation and said hydraulic motor is rigidly secured to said housing.
 11. The centrifuge of claim 1 including countIng means responsive to the rotation of said support means.
 12. The centrifuge of claim 1 wherein said support means includes an upwardly-open basket having cylindrical side walls with a plurality of perforations therein.
 13. The centrifuge of claim 1 including a holder for a plurality of batteries, said holder comprising:
 14. The centrifuge of claim 13 including stops on said first annular support surface to limit the pivotal movement of said battery cradles.
 15. The centrifuge of claim 13 including a centrally disposed circular web having a common axis with said annular support surface, said web being disposed inwardly and upwardly of said annular support surface, a plurality of elongated rigid members connecting said circular web and said annular support surface, and a hook receiving member secured to said web whereby the battery holder can be vertically lifted as a unit.
 16. The centrifuge of claim 13 wherein said battery support cradles have two upstanding partial walls on said lower horizontal web substantially perpendicular to and at the extremity of said upstanding wall, whereby a battery support pocket is formed.
 17. The centrifuge of claim 13 including bumpers having electrical insulation properties secured to the inner surface of said upstanding wall to electrically isolate the battery terminals during loading, unloading and centrifuging.
 18. The centrifuge of claim 13 wherein said battery holder includes at least a second annular support surface rigidly supported spacedly from said first annular support surface and having a common axis therewith, said second annular support surface having pivotally supported on upstanding rigid rod members thereof a plurality of battery cradles substantially identical to those on said first annular support surface, whereby a multi-tiered holder is provided.
 19. The centrifuge of claim 18 wherein the upstanding rigid rod members of said first and said second annular support surfaces are common.
 20. An electric-powered, variable-speed centrifuge suitable for heavy industrial loads comprising in combination: a. an outer shell with loading aperture; b. removable cover means for said aperture to provide access to the interior of said shell for loading and unloading purposes and to close said aperture during centrifuging operations; c. support means for the load to be centrifuged, said support means being rotatably mounted within said shell and accessible for loading and un-loading through said aperture; and d. drive means exterior of said shell for rotating said support means, said drive means comprising:
 21. The centrifuge of claim 19 including an adjustable pressure relief valve in the passageway between the outlet of said hydraulic motor and said adjustable throttle valve.
 22. The centrifuge of claim 21 including friction brakes for retarding rotation of said support means in cooperation with the dynamic braking of the hydraulic system, whereby a decrease in friction braking efficiency is reflected in prolongation of dynamic braking.
 23. The centrifuge of claim 19 including a multitiered battery holder disposed on said support means so as to be rotated by frictional engagement therewith. 